JP6332903B2 - Rubber composition for tire and pneumatic tire - Google Patents

Description

The present invention relates to a rubber composition for tires and a pneumatic tire using the same.

In recent years, the characteristics required of pneumatic tires for automobiles are diverse, including low fuel consumption (rolling resistance characteristics), wet grip performance (steering stability), and wear resistance. Various ideas have been made.

As a method for improving the wear resistance, for example, a method using natural rubber or butadiene rubber as a rubber component is known. However, when this method is used, wet grip performance tends to deteriorate. Moreover, as a method of achieving both wear resistance and wet grip performance, for example, there is a method of increasing the amount of reinforcing agent such as carbon black or silica. However, when this method is used, there is a tendency that the fuel efficiency is deteriorated. Thus, low fuel consumption, wet grip performance, and wear resistance are in a mutually contradictory relationship, and it has been difficult to improve these performances in a well-balanced manner.

Patent Document 1 discloses a triblock copolymer composed of a block segment of a styrene monomer unit and a block segment of a rubber monomer unit for the purpose of improving fuel efficiency while improving wear resistance. Although the technique mix | blended with a thing is disclosed (patent document 1), there exists room for improvement in the point of improving fuel-consumption property, wet grip performance, and abrasion resistance in a well-balanced manner.

JP 2004-2622 A

The present invention solves the above-mentioned problems, improves the fuel efficiency, wet grip performance and wear resistance in a well-balanced manner, and further provides good processability, and uses the rubber composition. It aims at providing the produced pneumatic tire.

The present invention contains a rubber component containing a styrene butadiene rubber having a styrene amount of 20% by mass or more, silica, and a styrene-butadiene-styrene block copolymer having a weight average molecular weight Mw of 5 × 10 ⁴ or more, In 100% by mass of the rubber component, the total content of the styrene-butadiene rubber and butadiene rubber is 90% by mass or more, and the content of the silica is 5 to 200 parts by mass with respect to 100 parts by mass of the rubber component. -It is related with the rubber composition for tires whose content of a butadiene-styrene block copolymer is 1-40 mass parts.

The amount of styrene in the styrene-butadiene-styrene block copolymer is preferably 1 to 50% by mass.

The weight average molecular weight Mw of the styrene-butadiene-styrene block copolymer is preferably 5 × 10 ⁴ to 2 × 10 ⁵ .

The styrene-butadiene rubber preferably has a styrene content of 20 to 60% by mass.

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, silica and a styrene-butadiene-styrene block having a weight average molecular weight Mw of a predetermined value or more with respect to a rubber component having a total content of styrene butadiene rubber and butadiene rubber having a high styrene content of a predetermined value or more. Since it is a rubber composition in which a predetermined amount of each copolymer is blended, it is possible to provide a pneumatic tire with improved fuel economy, processability, wet grip performance and wear resistance in a well-balanced manner.

The rubber composition for tires of the present invention includes a rubber component containing a styrene butadiene rubber having a styrene amount of 20% by mass or more, silica, and a styrene-butadiene-styrene block copolymer having a weight average molecular weight Mw of 5 × 10 ⁴ or more. (SBS), and the total content of the styrene butadiene rubber (SBR) and the butadiene rubber (BR) is 90% by mass or more in 100% by mass of the rubber component, with respect to 100 parts by mass of the rubber component. The silica content is 5 to 200 parts by mass, and the block copolymer content is 1 to 40 parts by mass.

By adding a predetermined amount of SBS having a weight average molecular weight Mw of a predetermined value or more to a rubber component having a high total content of SBR and BR having a high styrene content, compatibility between the rubber component and silica is improved. This can improve the fuel economy, workability, wet grip performance and wear resistance in a well-balanced manner.

SBS is a triblock copolymer composed of a styrene block, a butadiene block, and a styrene block, and can be synthesized by a general method. SBS may be modified with a compound having a polar functional group.

The amount of styrene in SBS is preferably 1% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, particularly preferably 25% by mass or more, and most preferably 30% by mass or more. If it is less than 1% by mass, sufficient interaction with silica cannot be obtained, and the fuel efficiency tends to deteriorate. The amount of styrene in SBS is preferably 50% by mass or less, more preferably 40% by mass or less. If it exceeds 50% by mass, kneading becomes difficult and sufficient workability may not be ensured.

In the SBS, the ratio (molar ratio) of the styrene blocks that sandwich the butadiene block is preferably 1: 1. That is, the SBS preferably has a symmetrical structure with the butadiene block as the center. Thereby, the compatibility of the rubber component and silica can be improved, and the occurrence of poor dispersion of silica can be suppressed.

The weight average molecular weight Mw of SBS is 5.0 × 10 ⁴ or more, preferably 6.0 × 10 ⁴ or more, more preferably 7.0 × 10 ⁴ or more, and particularly preferably 1.0 × 10 ⁵ or more. If it is less than 5.0 × 10 ⁴ , wet grip performance, wear resistance and fuel efficiency may be deteriorated. The weight average molecular weight Mw of SBS is preferably 2.0 × 10 ⁵ or less, more preferably 1.5 × 10 ⁵ or less, and still more preferably 1.3 × 10 ⁵ or less. If it exceeds 2.0 × 10 ⁵ , kneading becomes difficult, and sufficient workability may not be ensured.
In the present invention, Mw is a value converted from standard polystyrene using GPC.

The content of SBS is 1 part by mass or more, preferably 5 parts by mass or more, more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 1 part by mass, the effect of improving the compatibility is not sufficient, and the wear resistance tends not to be sufficiently improved. The SBS content is 40 parts by mass or less, preferably 30 parts by mass or less, more preferably 20 parts by mass or less. If it exceeds 40 parts by mass, the physical properties of the rubber will be lowered, and there is a tendency that an effect commensurate with the increase in cost cannot be obtained.
In the present invention, SBS is used as an additive and is not included in the rubber component.

The rubber composition of the present invention contains SBR having a high styrene content and, if necessary, BR as rubber components. The total content of SBR and BR in 100% by mass of the rubber component is 90% by mass or more, preferably 95% by mass or more, more preferably 99% by mass or more, and further preferably 100% by mass. If it is less than 90% by mass, the amount of rubber other than SBR and BR, such as natural rubber (NR), is large, so that the compatibility of the rubber component is lowered, and there is a risk of interfacial peeling.

The amount of styrene in SBR is 20% by mass or more, preferably 24% by mass or more, more preferably 28% by mass or more, still more preferably 30% by mass or more, preferably 60% by mass or less, more preferably 50% by mass or less. Further, it is more preferably 45% by mass or less, particularly preferably 40% by mass or less. If it is in the said range, low-fuel-consumption property, wet grip performance, and abrasion resistance will be obtained with sufficient balance.

The content of SBR in 100% by mass of the rubber component is preferably 35% by mass or more, more preferably 45% by mass or more, and preferably 85% by mass or less, particularly preferably 80% by mass or less. If it is in the said range, low-fuel-consumption property, workability, wet grip performance, and abrasion resistance will be obtained with good balance.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B and other high cis content BR; VCR412 manufactured by Ube Industries, Ltd., VCR617, etc. Commonly used in the tire industry such as BR containing syndiotactic polybutadiene crystals can be used.

The content of BR in 100% by mass of the rubber component may be 0% by mass, but is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. If it is less than 5% by mass, fuel economy tends to deteriorate. The content of BR is preferably 60% by mass or less, more preferably 50% by mass or less. When it exceeds 60 mass%, there exists a tendency for abrasion resistance to deteriorate.

The rubber composition of the present invention contains silica as a filler. Examples of the silica include, but are not limited to, dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and wet process silica is preferable because of its large number of silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 40 m ² / g or more, more preferably 50 m ² / g or more, still more preferably 100 m ² / g or more, and particularly preferably 150 m ² / g or more. If it is less than 40 m ² / g, the fracture strength after vulcanization is lowered, and there is a possibility that sufficient wear resistance cannot be ensured. The N ₂ SA of silica is preferably 500 m ² / g or less, more preferably 300 m ² / g or less. If it exceeds 500 m ² / g, fuel economy and processability tend to deteriorate.
The _N 2 SA of silica is a value measured by the BET method in accordance with ASTM D3037-81.

The content of silica is 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. It is. If the amount is less than 5 parts by mass, sufficient fuel economy may not be ensured. The content of silica is 200 parts by mass or less, preferably 150 parts by mass or less, more preferably 100 parts by mass or less. When the amount exceeds 200 parts by mass, it is difficult to disperse silica, and the workability tends to deteriorate.

The rubber composition of the present invention preferably contains a silane coupling agent together with silica. Although it does not specifically limit as a silane coupling agent, For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (3- Trimethoxysilylpropyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxy Silylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole Sulfide systems such as tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane Mercapto type such as 2-mercaptoethyltriethoxysilane; Vinyl type such as vinyltriethoxysilane and vinyltrimethoxysilane; Amino systems such as nopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane; γ-glycid Glycidoxy systems such as xylpropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane; 3-nitropropyltrimethoxysilane, 3 -Nitro type such as nitropropyltriethoxysilane; chloro type such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, etc.Moreover, as a mercapto type | system | group, NXT by the Momentive company which has the structure where the mercapto group was protected, NXT-Z, etc. can be used. One of these silane coupling agents may be used alone, or two or more thereof may be used in combination.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 1 part by mass, the viscosity of the unvulcanized rubber composition is high, and the processability tends to deteriorate. The content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less. When it exceeds 20 parts by mass, there is a tendency that an effect commensurate with the increase in cost cannot be obtained.

The rubber composition of the present invention preferably contains carbon black as a filler. Thereby, wet grip performance and wear resistance can be further improved. Carbon black is not particularly limited, and those generally used in the tire industry such as SAF, ISAF, HAF, FF, GPF can be used.

The average particle size of carbon black is preferably 31 nm or less, more preferably 25 nm or less, and still more preferably 23 nm or less. If it exceeds 31 nm, the breaking strength is greatly deteriorated, and sufficient wear resistance may not be ensured. The average particle size of carbon black is preferably 15 nm or more, more preferably 19 nm or more. If it is less than 15 nm, the viscosity of the blended rubber is significantly increased, and the processability may be deteriorated.
In addition, the average particle diameter of carbon black is a number average particle diameter, and is measured with a transmission electron microscope.

Carbon black has a dibutyl phthalate (DBP) oil absorption of preferably 100 ml / 100 g or more, more preferably 105 ml / 100 g or more, and even more preferably 110 ml / 100 g or more. If it is less than 100 ml / 100 g, the reinforcing property is low, and it may be difficult to ensure wear resistance. The DBP oil absorption of carbon black is preferably 160 ml / 100 g or less, more preferably 150 ml / 100 g or less. When it exceeds 160 ml / 100 g, it becomes difficult to produce carbon black itself.
In addition, the DBP oil absorption amount of carbon black is calculated | required by the measuring method of JISK6217-4.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 80 m ² / g or more, more preferably 90 m ² / g or more. If it is less than 80 m ² / g, the breaking strength is greatly deteriorated, and sufficient wear resistance may not be ensured. The N ₂ SA of carbon black is preferably 200 m ² / g or less, more preferably 150 m ² / g or less. When it exceeds 200 m ² / g, the viscosity of the blended rubber is significantly increased, and the processability may be deteriorated.
The N ₂ SA of carbon black is determined by the A method of JIS K6217.

The content of carbon black is preferably 2 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 2 parts by mass, the reinforcing property is low, and sufficient wear resistance may not be ensured. The content of carbon black is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 15 parts by mass or less. If it exceeds 50 parts by mass, the fuel efficiency tends to deteriorate.

The silica content (content) in the total of 100% by mass of silica and carbon black is preferably 50% by mass or more, more preferably 55% by mass or more. If it is less than 50% by mass, sufficient fuel economy and wet grip performance may not be ensured. The silica content is preferably 95% by mass or less. If it exceeds 95 mass%, sufficient wear resistance and workability may not be ensured.

The rubber composition of the present invention may contain other fillers in addition to silica and carbon black. Examples of other fillers include, but are not limited to, calcium carbonate, aluminum hydroxide, montmorillonite, cellulose, various short fibers, glass balloons, eggshells, and the like.

In addition to the components described above, the rubber composition of the present invention can appropriately contain a wax, an antioxidant, stearic acid, zinc oxide, sulfur, a vulcanization accelerator, and the like.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a kneader such as a Banbury mixer, a kneader, or an open roll, and then vulcanizing.

When the additives other than the vulcanizing agent and the vulcanization accelerator are blended, the kneading temperature is usually 50 to 200 ° C., preferably 80 to 190 ° C., and the kneading time is usually 30 seconds to 30 minutes. It is preferably 1 minute to 30 minutes. When blending a vulcanizing agent and a vulcanization accelerator, the kneading temperature is usually 100 ° C. or lower, preferably room temperature to 80 ° C.

A composition containing a vulcanizing agent and a vulcanization accelerator is usually used after vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 120 to 200 ° C, preferably 140 to 180 ° C.

The rubber composition of this invention can be used for each member of a tire, and can be used conveniently for a tread.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, by extruding a rubber composition containing the above components in accordance with the shape of a tread or the like at an unvulcanized stage, and molding it with a tire molding machine by a normal method along with other tire members, Form an unvulcanized tire. The pneumatic tire of the present invention can be manufactured by heating and pressurizing the unvulcanized tire in a vulcanizer.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in the synthesis of the block copolymer (SBS) will be described together. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
n-hexane: Kanto Chemical Co., Ltd. Styrene: Kanto Chemical Co., Ltd. 1,3-Butadiene: Tokyo Chemical Industry Co., Ltd. Tetrahydrofuran: Wako Pure Chemical Industries, Ltd. n-Butyllithium: Kanto Chemical Co., Ltd. 1.6M n-butyllithium hexane solution 2,6-tert-butyl-p-cresol manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

<Analysis of block copolymer>
The block copolymer obtained by the following was analyzed by the following method. The analysis results are shown in Table 1.

(Measurement of weight average molecular weight Mw)
The weight average molecular weight Mw of the block copolymer was determined by gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation), detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation. ) Based on standard polystyrene conversion.

(Structural identification of block copolymer)
The structure of the block copolymer was identified using an AV400 apparatus manufactured by BRUKER. From the measurement results, the amount of styrene in the block copolymer was calculated.

<Synthesis of block copolymer>
(Block copolymer 1)
In a heat-resistant container sufficiently purged with nitrogen, 1500 ml of n-hexane, 0.37 mol of styrene, and 0.2 mmol of tetrahydrofuran were added, and the temperature was raised to 40 ° C. Next, 2.3 mmol of n-butyllithium was added, and then the temperature was raised to 50 ° C. and stirred for 1 hour. Next, 2.2 mol of 1,3-butadiene was added and stirred for 30 minutes. Thereafter, 0.37 mol of styrene was added and stirred for 1 hour. Thereafter, alcohol was added to stop the reaction, 1 g of 2,6-tert-butyl-p-cresol was added to the reaction solution, and then a block copolymer 1 was obtained by reprecipitation purification. The obtained block copolymer 1 had a weight average molecular weight Mw of 100,000 and a styrene content (styrene component content) of 40% by mass.

(Block copolymer 2-4)
According to the formulation of Table 1, it was synthesized by the same method as that for the block copolymer 1.

Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
SBR1: Nipol NS522 manufactured by Nippon Zeon Co., Ltd. (styrene content: 39% by mass, oil spreading ratio: containing 37.5 parts by mass of oil with respect to 100 parts by mass of rubber component, Table 2 shows the amount of only rubber component Description)
SBR2: SL574 manufactured by JSR Corporation (styrene content: 15% by mass)
BR: Ubepol BR150B manufactured by Ube Industries, Ltd.
NR: RSS # 3
Block copolymers 1-4: Synthetic silica by the above method: Ultrasil VN3 (N ₂ SA: 175 m ² / g) manufactured by Degussa
Carbon black: Dia Black N339 manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 96 m ² / g, DBP oil absorption: 124 ml / 100 g, average particle size: 26 nm)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Oil: X-140 manufactured by Japan Energy Co., Ltd.
Wax: Sunnock N manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Stearic acid “paulownia” manufactured by NOF Corporation
Zinc oxide: Zinc Hua 1 anti-aging agent manufactured by Mitsui Mining & Smelting Co., Ltd .: NOCRACK 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. )
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. 1: Noxeller CZ manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator 2: Noxeller D from Ouchi Shinsei Chemical Co., Ltd.

<Examples and Comparative Examples>
According to the blending content shown in Table 2, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150 ° C. using a 1.7 L Banbury mixer manufactured by Kobe Steel Co., Ltd. Obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.

The obtained unvulcanized rubber composition and vulcanized rubber composition were evaluated for processability, fuel efficiency, wet grip performance and wear resistance by the following test methods. The results are shown in Table 2.

<Evaluation items and test methods>
(Processability)
Based on JIS K6300-1, the Mooney viscosity (ML _{1 + 4} ) of the above-mentioned unvulcanized rubber composition was measured at 130 ° C., and the measurement result was displayed as an index by the following formula. The larger the index, the better the processability when unvulcanized.
(Processability index) = (Mooney viscosity of Comparative Example 1) / (Mooney viscosity of each formulation) × 100

(Low fuel consumption)
Using a spectrometer manufactured by Ueshima Seisakusho, tan δ of the vulcanized rubber composition was measured at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50 ° C., and the measurement results were indicated by an index using the following formula. The larger the index, the lower the rolling resistance and the better the fuel efficiency.
(Low fuel consumption index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Wet grip performance)
Wet grip performance was evaluated using a flat belt friction tester (FR5010 type) manufactured by Ueshima Seisakusho. A cylindrical rubber test piece having a width of 20 mm and a diameter of 100 mm made of the above vulcanized rubber composition was used as a sample, and the slip ratio of the sample with respect to the road surface was 0 to 0 at a speed of 20 km / hour, a load of 4 kgf, and a road surface temperature of 20 ° C. The maximum value of the friction coefficient detected at that time was read up to 70%. And the measurement result was displayed as an index according to the following formula. A larger index indicates better wet grip performance.
(Wet grip performance index) = (maximum friction coefficient of each formulation) / (maximum friction coefficient of Comparative Example 1) × 100

(Abrasion resistance)
Using a Lambone-type wear tester, the Lambourne wear amount of the vulcanized rubber composition was measured under the conditions of room temperature, applied load of 1.0 kgf, and slip rate of 30%. The volume loss amount was calculated from the measured Lambourn wear amount, and the volume loss amount of each formulation was indicated by an index using the following formula. It shows that it is excellent in abrasion resistance, so that an index | exponent is large.
(Abrasion resistance index) = (volume loss amount of Comparative Example 1) / (volume loss amount of each formulation) × 100

As shown in Table 2, the rubber compositions of the examples blended with a predetermined amount of the block copolymer have processability, low fuel consumption, wet grip performance and wear resistance as compared with the rubber compositions of the comparative examples. Improved in a well-balanced manner. In particular, in Example 1 in which the block copolymer 1 having a large amount of styrene was blended, excellent performance was obtained.

In Comparative Example 2, the content of the block copolymer was too much, and the processability and fuel efficiency were greatly deteriorated. In Comparative Example 3, the content of SBR and BR was reduced by the blending of NR, so that the wet grip performance was greatly deteriorated despite blending a predetermined amount of the block copolymer. The comparative example 4 which mix | blended the block copolymer 4 with a small weight average molecular weight Mw is inferior in fuel-consumption property, wet grip performance, and abrasion resistance compared with Example 1, and wet grip performance and abrasion resistance are It was inferior to the comparative example 1 used as a reference. In Comparative Example 5 in which SBR2 containing a small amount of styrene was blended, the processability was good, but the fuel economy, wet grip performance and wear resistance were greatly deteriorated.

Claims (3)

A rubber component containing styrene butadiene rubber and butadiene rubber having a styrene amount of 20 to 60% by mass, silica, and a styrene-butadiene-styrene block copolymer having a weight average molecular weight Mw of 1 × 10 ⁵ to 2 × 10 ^5. Contains,
In 100% by mass of the rubber component, the total content of the styrene butadiene rubber and the butadiene rubber is 90 to 100% by mass, the content of the styrene butadiene rubber is 45 to 85% by mass, and the content of the butadiene rubber is 10 to 10%. 50% by weight,
A rubber composition for a tire, wherein the content of the silica is 5 to 200 parts by mass and the content of the styrene-butadiene-styrene block copolymer is 1 to 40 parts by mass with respect to 100 parts by mass of the rubber component. The tire rubber composition according to claim 1, wherein the styrene-butadiene-styrene block copolymer has a styrene content of 1 to 50 mass%. A pneumatic tire produced using the rubber composition according to claim 1.